In various industries, point sensors are installed at various intervals along optical fibers that span long distances, e.g. from hundreds of meters to tens of kilometers. One type of sensor measures environmental parameters through the change in the spectral optical loss of the sensor. These sensors usually work at a number of different wavelengths, often tens to one or two hundred nanometers apart. Spectral losses, i.e. optical losses that vary with wavelength, and spectral loss stability in the fiber link then become important factors. In order to measure spectral loss in point sensors installed along optical fibers, often of great lengths, time evolution techniques such as fluorescence lifetime technique or ring down spectroscopy are usually used. These techniques can be time-consuming or require low-dispersion fibers which are inadequate in coupling thereto several sensors.
Therefore, there is a need for an improved optical sensing method and system.